Integrated optical system for endoscopes and the like

Abstract

Optical systems for endoscopes, borescopes, dental scopes, and the like which are characterized by having three groups of lenses of positive optical power and an external entrance pupil. Typically, all three groups of lenses are displaced from the pupil and focal planes. As a consequence, the displaced groups take part in the image transfer as well as in the pupil transfer. The optical power requirements can thus be shifted from one group to another, distributing as well as reducing the overall power requirement. Moreover, the aberration correction can also be shared between these groups. The first group, which conventionally has the highest optical power, and consequently a large amount of aberrations to be corrected, can in this way transfer some of the optical aberration correction to the other groups. The sharing of the optical functions and aberration correction results in a fully integrated optical system. The reduction in the total amount of optical power is so large that a line-of-sight deviating prism can be readily accommodated between the entrance pupil and the first lens group. The resulting simplicity of the optical system makes it suitable as a disposable item.

Having thus described the invention I claim:  
     
         1 . An endoscopic optical system extending along an optical axis comprising: 
 at least three spaced-apart groups of optical elements of uniform refractive index disposed serially along the optical axis for the transfer of an image from an input focal plane to an output focal plane, each of said at least three groups being of positive optical power and having at least one element, and    means defining an entrance pupil at an entrance pupil plane which is positioned between the input focal plane and the nearest one of said three groups.    
     
     
         2 . An endoscopic optical system of  claim 1  wherein a focal plane or pupil plane exists between a majority of the pairs of adjacent ones of said-at least three groups.  
     
     
         3 . An endoscopic optical system of  claim 1  wherein each of said three groups is spaced from each of the focal and pupil planes.  
     
     
         4 . An endoscopic optical system of  claim 3  wherein each of said at least three groups has a maximum radial width and is spaced from at least one adjacent focal or pupil plane by a distance greater than the maximum radial width of that group.  
     
     
         5 . An endoscopic optical system of  claim 1  further comprising an optical axis-bending means disposed between said entrance pupil and said one of said groups.  
     
     
         6 . An endoscopic optical system of  claim 1  wherein each element in each of said groups has surfaces and each of said surfaces has a curvature, and the sum of the absolute values of the curvatures of all said elements in said at least three groups is less than 1.5.  
     
     
         7 . An endoscopic optical system of  claim 8 , further comprising a fourth one of said at least three groups having at least one element with surfaces with curvatures, and the sum of the absolute values of the curvatures of said said four groups is less than 1.5.  
     
     
         8 . An endoscopic optical system of  claim 1  wherein said at least three groups have elements with positive power which produce an image on an output focal plane having an axial color aberration of less than 0.8 waves.  
     
     
         9 . An endoscopic optical system of  claim 1  wherein only one of said elements in said at least three groups has negative power.  
     
     
         10 . An endoscopic optical system of  claim 11  wherein only one of said elements in said at least three groups produce an image on an output focal plane having an axial color aberration of less than 0.5 waves.  
     
     
         11 . An endoscopic optical system of  claim 1  wherein each of said elements is made of plastic.  
     
     
         12 . An endoscopic optical system of  claim 1  wherein each of said at least three groups consists of a single element of positive optical power.  
     
     
         13 . An endoscopic optical system of  claim 1  further comprising a rodshaped element.  
     
     
         14 . An endoscopic optical system of  claim 1  further comprising a first relay assembly for transmitting an image focussed on the output focal plane to a first downstream focal plane, said relay assembly comprising a plurality of elements, with only one element in said at least three groups and said relay assembly having negative power.  
     
     
         15 . An endoscopic optical system of  claim 16  further comprising a second of said relay assemblies for transmitting an image focussed at the first downstream focal plane to a second downstream focal plane, with only one element in said at least three groups and said first and second relay assemblies having negative power.  
     
     
         16 . An endoscopic optical system of  claim 1  consisting of said three groups and a fourth group consisting of a single element of a power less than any of the other elements.  
     
     
         17 . An endoscopic optical system extending along an optical axis comprising: 
 three spaced-apart groups of optical elements of uniform refractive index disposed serially along the optical axis for the transfer of an image from an input focal plane to an output focal plane, each group having positive power, having at least one element, and being spaced from each of the focal and pupil planes, each of said elements having surfaces with curvatures with the sum of the absolute values of the curvatures of said elements being less than 1.5, said groups collectively producing an image on the output focal plane, with only one of said elements having negative power and said three groups producing an image at the output focal plane having an axial color aberration of less than 0.8 waves, and    means defining an entrance pupil at an entrance pupil plane that is positioned between the input focal plane and the first group, and light travels substantially directly between the input focal plane and said entrance pupil.